1. Field of the Invention
The present invention relates to a projector, and more particularly, it relates to a projector having a light tunnel.
2. Description of the Background Art
A projector having a light tunnel for forming light from a source lamp into a prescribed shape is known in general, as disclosed in Japanese Patent Laying-Open No. 2004-354925, Japanese Utility Model Registration No. 3093005, Japanese Utility Model Registration No. 3092510 or Japanese Patent Laying-Open No. 2005-43603. Each of Japanese Utility Model Registration No. 3092510 and Japanese Patent Laying-Open No. 2005-43603 proposes a light tunnel clip for holding the light tunnel on the projector. On the other hand, Japanese Patent Laying-Open No. 2004-354925 and Japanese Utility Model Registration No. 3093005 disclose no light tunnel clips.
FIG. 17 is a perspective view of a casting 100 mounted with a light tunnel 101 of the conventional projector disclosed in Japanese Utility Model Registration No. 3092510. FIG. 18 is a perspective view of a conventional light tunnel clip 102 disclosed in Japanese Utility Model Registration No. 3092510. FIG. 19 is a perspective view of the conventional light tunnel clip 102 disclosed in Japanese Utility Model Registration No. 3092510 mounted on the casting 100. The structure of a portion around the light tunnel 101 of the conventional projector disclosed in Japanese Utility Model Registration No. 3092510 is now described with reference to FIGS. 17 to 19.
As shown in FIG. 17, the casting 100 is provided with a groovelike holding portion 100a holding the light tunnel 101 (see FIG. 19). The casting 100 is also provided with a pair of threaded holes 100b receiving a pair of screws 103 (see FIG. 19) for mounting the light tunnel clip 102 (see FIG. 18) thereon. The casting 100 is further provided with a pair of bosses 100c for positioning the light tunnel clip 102.
As shown in FIG. 18, the light tunnel clip 102 is provided with pressing portions 102a, 102b, 102c and 102d pressing the outer surfaces of the light tunnel 101 against the holding portion 100a of the casting 100. As shown in FIG. 19, the pressing portions 102a and 102b are so formed as to press a first surface 110a of the light tunnel 101, while the pressing portions 102c and 102d are so formed as to press a second surface 101b of the light tunnel 101. The light tunnel clip 102 is provided with a pair of positioning holes 102e for fitting with the pair of positioning bosses 100c of the casting 100 respectively. The light tunnel clip 102 is also provided with a pair of screw receiving holes 102f receiving the pair of screws 103 for mounting the light tunnel clip 102 on the casting 100 respectively. The light tunnel clip 102 is further provided with a mask portion 102g for screening the outer periphery of an inlet of the light tunnel 101 from light.
When the light tunnel 101 is arranged on the holding portion 100a of the casting 100, the positioning bosses 100c of the casting 100 are fitted into the positioning holes 102e for positioning the light tunnel clip 102, and the two screws 103 are inserted into the screw receiving holes 102f. The light tunnel clip 102 mounted on the casting 100 presses the first surface 101a of the light tunnel 101 toward the holding portion 100a of the casting 100 with the pressing portions 102a and 102b, while pressing the second surface 101b of the light tunnel 101 also toward the holding portion 100a of the casting 100 with the pressing portions 102c and 102d. 
Japanese Patent Laying-Open No. 2005-43603 discloses a projector having a light tunnel clip, similar to that disclosed in Japanese Utility Model Registration No. 3092510, provided with a stop member for easily registering relative positions of a lamp case storing a source lamp and a light tunnel.
In each of the projectors according to Japanese Patent Laying-Open No. 2005-43603 and Japanese Utility Model Registration No. 3092510, however, the pressing portions 102a, 102b, 102c and 102d of the light tunnel clip 102 press different positions P5, P6, P7 and P8 of the light tunnel 101 in the traveling direction of light L respectively, as shown in FIG. 19. Therefore, pressing force nonuniformly acts on the light tunnel 101 in the traveling direction of the light L. Thus, the position of the light tunnel 101 disadvantageously shifts due to vibration of a motor or the like provided on the projector.